The present invention relates to specific photochromic 3H-naphtho[2,1-b]pyran compounds and their use in synthetic resin materials (i.e., plastics) of all types, in particular for ophthalmic purposes. The present invention relates in particular to photochromic compounds derived from 3H-naphtho[2,1-b]pyrans which have especially long wavelength absorption maximums in the open form, so that when used in phototropic glasses, essentially blue tones can be achieved which have a high darkening performance at the same time.
Various classes of dyes are known which undergo a reversible change in color on exposure to light of certain wavelengths. This is due to the fact that these dye molecules are converted to an excited colored state by input of energy in the form of light and leave this state again when the input of energy is interrupted, so that they return to their colorless or at least barely colored normal state. These phototropic dyes include, for example, naphthopyrans, which have already been described in the state of the art with various substituents.
Pyrans, specifically naphthopyrans and larger ring systems derived from them are photochromic compounds which have so far been the object of intense investigations. Although the first patent for these compounds was applied for in the year 1966 (U.S. Pat. No. 3,567,605), it was not until the 1990s that compounds suitable for use in eyeglasses were developed.
The dyes known in the prior art often have an inadequate long wavelength absorption in the excited state as well as in the unexcited state. In combinations with other photochromic dyes, this leads to problems. In addition, there is often too great a sensitivity with regard to the darkening effect, and the brightening takes place too slowly. In addition the dyes available in the state of the art often have an inadequate lifetime. Consequently, such sunglasses do not have an adequate stability. The latter is manifested in a rapid decline in performance and/or severe yellowing.
3H-Naphthopyrans derived from 2-naphthols and similar higher derivatives derived by annellation are a group of photochromic dyes whose longest wavelength absorption maximum of the excited form is mainly in the spectral range from 420 nm to 500 nm and thus they impart a yellow, orange or reddish orange color impression (see U.S. Pat. Nos. 5,869,658 and 6,022,495). For neutral darkening phototropic glasses, however, powerful blue to violet photochromic dyes are needed. Blue to violet photochromic dyes currently available in the state of the art usually come from the class of spiroxazines, fulgides or 2H-naphtho[1,2-b]pyrans. However, spiroxazine dyes are usually at a disadvantage with regard to high temperature performance, whereas fulgide dyes do not have completely satisfactory properties in terms of their lifetime and 2H-naphtho[1,2-b]pyrans do not have fully satisfactory properties with regard to their rate of lightening for use in sunglasses.
Introducing electron shifting substituents on the aryl groups in o-position to the pyran oxygen as described in WO 98/45281, WO 01/12619 and European Patent No. EP 945,451, for example, leads to 3H-naphtho[2,1-b]pyrans that darken to a red or reddish violet shade. WO 01/12619 discloses compounds whose one geminal aryl group has a para-amino-substituted group and whose other aryl group has an alkoxy or thioalkoxy group with a substituent in meta- or para-position; this substitution pattern has a positive influence on the rate of lightening. WO 98/45281 describes red hyperchromic compounds which also have an amine function mainly in position 6 on the 3H-naphtho[2,1-b]pyran unit. Compounds which do not have pronounced basic amino groups are described in European Patent No. EP 945,451; these compounds have a pinkish to violet color in the excited state and also have an attractive lifetime performance. WO 99/31082 also discloses 3H-naphtho[2,1-b]pyrans with aryl substituents in position 6. The effect of the aryl substitution in position 6 on the longest wavelength absorption maximum of the excited and unexcited forms is very minor with these compounds, however.
Corresponding substitution in the 8-position of the 3H-naphtho[2,1-b]pyran unit produces a bathochromic shift of the longest wavelength absorption maximum, especially by introduction of alkoxy groups as described in U.S. Pat. No. 5,238,981. In addition, compounds with dialkylamino groups in the 8-position have also been disclosed. The use of nitrogen heterocycles as substituents in position 8 of the 3H-naphtho[2,1-b]pyran unit is mentioned in U.S. Pat. No. 5,990,305, so that an improved lifetime is achieved in contrast with open-chain amino groups. This is also achieved with substituents containing so-called HALS (hindered amine light stabilizer) structure units. Finally, published German Patent application no. DE 102 00 040 describes blue to violet 3H-naphtho[2,1-b]-pyrans which have substituents with amino groups in positions 3 and 8.